Method of operating flaming-arc lights for projectors



P. R. BASSETT.

METHOD OF OPERATING FLAMING ARC LIGHTS FOR PROJECTORS.

APPLICATION FILED DEC-18,1916.

1,328,311, Patented Jan. 20, 1920.

Fig. 5

- INVENTOR PRESTON R. BASSE T T.

' Improvements in Methods of Operating.

UNITED STATES PATENT OFFICE.

PRESTON BASSETT, OF BROOKLYN, NEW YORK, ASSIGNOR TO ELMER A. SPERRY, OF

BROOKLYN, NEW YORK.

METHOD OF OPERATING FLAMING-ARC LIGHTS FOR PROJECTORS.

' To all whom it mayv concern:

Be it known that I, PRESTON R. BASSETT, a citizen of the United States of America, residing at 1716 Newkirk avenue, Brookl n, in the county of Kings and State of ew York, have invented certain new and useful Flaming-Arc Lights for Projectors, of which 1 the following is a specification.

This invention relates to an lmproved method of operating a moderate amperage and moderate-voltage high intensity direct current arc suitable for projector work. I refer to amperages of from 4:0 to 100 and voltages of from 40 to 50 or thereabout.

- The basis of searchlight efiiciency is primarily intrinsic brilliancy at the source. The object accomplished by this invention is the increase of the intrinsic brilliancy" of the positive crater to a point higher than can be obtained by either black body radiation or incandescence of any known material.

While'I am aware that high intensity flaming arcs havebeen obtained heretofore by the method of operating outlined in the U, S. patent to Elmer A. Sperry, 1,227 ,210,

dated May 22, 1917, such a method requires as a rulemuch greater power than an arc operated according to my invention. While such method may be employed .and the high intensity phenomena retained at comparatively moderate currents with good results, my invention furnishes an alternative or modified method of operation for moderate currents (i. e. in the neighborhood of 40 to 90 amps.) which possesses the great advantage of burning at a much lower voltage than an are operated according to sald' Sperry patent and thereby effect a saving in power consumed, although at a slightsacrifice ofcandlepower.

Referring to the drawings which show diagrammatically the principle underlying my invention, Figure 1 is a side elevation of a pair of flamlng arc electrodes operating at a comparatively short arc length according to existing practices.

Fig. 2 is a similar view showing the behavior of the flame or flames. at a greater arc length.

Fig. 3 is a similar view of electrodes op erating according tomy invention.

Fig. 4 is a front view .of the same. Fig. 5 is a front view-showing the effect of increasing the arc length.

Specification of Letters Patent. f

Patented Jan. 20, 1920.

Application filed December 18, 1916. Serial No. 137,743.

Both electrodes under this invention are preferably cored carbons. The positive electrode P comprises a pure carbon shell 1 and a core 2 the latter containing a mixture withvent wandering thereof. For the sake of brevity, the electrodes may be referred to as flaming arc electrodes.

Both carbons are run at moderate or even high current density, the positive electrode being in the neighborhood of 1} an inch in diameter. In operating electrodes as above described at the specifiedcurrents of from 40-to 90 amperes, it is found that the desired results cannot be obtained with any ordinary electrode arrangement used at the present time in searchlights.

In securing the desired results the problem has been to maintain the positive crater 7 continuously at what might be called abnormal brilliancy. The arc'with ordinary electrode arrangemenflsuch, for instance, as is shown in Figs. 1 and 2 tends to be un steady, and'the positive crater at times fails to produce the high intensity kernel 9 characteristic of my invention and suddenly appears almost black instead of giving the desired blue-white intense light. It is necessary', of course, that this kernel of intense light-be permanent, dependable, and not sensitive. I l

"I have discovered that in order to maintain this intense light at the low currents and voltages employedthe followingare important essentials:

1st. The impregnated core 2 of the positive electrode should be run at a current density-at its crater face, which is higher than it would normally run, 11. a, the coreface should be overloaded continuously so that if the arc were burned in the usual manner the flame would overflow and emanate from the shell and especially the outer walls of the electrode tip. To accomplish this,'I employ a small positive electrode and adjust the amount of this spindling of the shell so that at the crater there is only enough shell surrounding'the core to prevent the oxidation of the core. In order to prevent the spindling from extendingback too far I may employ a heat resisting and preferably also insulating sleeve '11 to surround the electrode adjacent the arc of quartz .or the like. This sleeve stops a predetermined distance back of the arc, as shown. It not only prevents oxidation and vaporization of the carbon within, but also aids in maintaining the heat of the arc by preventing heat losses close to the arc.-

2nd. In order to confine and maintain this current overload to the core face itis necessary to prevent the negative arc flame 5 from having any chance oftouching other parts of the positive electrode. It should be confined to th'e crater face itself.

The crater forming a part of this invention, running at an abnormal current density as itdoes, has a strong tendency to spread,

thus reducing the current density to the normal figure at which figure the desired results are lost. Special steps should there fore be taken to diminish the part played Ibythe shell of the positive carbon in the formation of the are proper. Marked spindling, preferably produced by oxidation is therefore important in causing the core to protrude forward so that the flame may establish the necessary circuit relation,

thereby, insuring the necessary energy concentration at the core face for producing the high intensity light spot or kernel. In fact the arc flame must not be allowed to touch parts of the electrode other than this core face, and the very thin protecting shell around the core face. My preferred method of accomplishing this result is to tilt the negative carbonat a large angle. Figs. 1 and2 show the tendency of this arc. under ordinary conditions to are from other portions of the positive electrode than the crater face, Fig. 1 showing the burning conditions when a short arc is employed and Fig. 2 the conditions with the longer arc. By this or equivalent means the arc flame5 which according to my invention appears to emanate almost entirely from the negative electrode, passes almost vertically past the positive electrode as though nothing but the least the positive electrode though this is by no means necessary.

The electrode may be tilted as much as from 15 to GO'degrees below the horizontal, thus producing as stated an almost vertical negative arc flame. This position of the arc' able gains are made thereby, such as, mainend of the core were present. The tip 8 of a the negative is preferably positioned slightly face of the positive core surrounded .by a

thin rim of the shell is touched by the flame (Figsp3 and 4) In order to secure uniform tapering of the desired characteristics as hereinafter specified, I prefer to rotate at taining a constant axial position of the light source, as well as securing a uniform spindling of the electrode, and promoting such spindling asa concave curve 6, of the outer walls instead of a convex curve, as is usual with a carbon arc.

3rd. The third important factor in my invention relates somewhat to the second, as it has been found. an effective aid in preventing the spreading of the crater. This is the use of a very short arc, say under 3,- of an inch. If attempt is made to employ a short are with the ordinary electrode arrange- 3 ment, an arc such as shown in Fig. 1 is produced in which the negative flame envelops the tip of the positive.

With my arrangement, however, a low voltage arc is obtained with slowconsumption of the positive electrode, which burns in such a manner as to cause definite spindling while presenting a very shallow crater that in point of diameter closely approxi- 'mates that of the core. In the operation of this arc av small high intensity spot of blue-' white light is maintained at the positive crater, which as stated, is about coextensive with the core of theelectrode. J

The advantage of theshort arc with my electrode arrangement is that the particular portion of the flame which contacts with or finds itself supplying the sole circuit connection with the positive crater is of about the same diameter as such crater as shown in Fig. 4. This is indicated by the fact that if the are be increased in length the negative flame at the point of contact with the crater becomes wider than the crater (Fig. 5) causing unsteadiness, spreading of the arc, energy dissipation of thekernel and occasional periods of a black crater I Another advantage of the short are is that it materially increases the stability of the arc andits resistance to drafts. In the direct current are of from 40 to 90 amperes, the arc flame is of'low velocity when compared to arcs burning over 100 amperes. It is therefore most suitable to have as short a length of arc flame between the electrodes as possible, since it is very susceptible to air currents when the arc length is much longer than specified above.

It is to be noticed that another radical difference exists between this high intensity arc and the forms previously known. The latter, in fact, all other known high intensity arcs have an arc voltage higher than the ordinary arc, whereas this high intensity arc has an arc voltage lower than the ordinary arcto illustrate:

The hereinbefore referred to Sperry high intensity are burning from 70 to 200 amperes has an arc voltage of from 60 to 85 volts as compared to an ordinary arc voltage of this amperage of about to volts. This new form of high intensity are at amperes below 100 in one of its satisfactory embodiments .has an arc voltage of only about 4:2 to 45 volts.

My invention is in many ways distinguished from the aforesaid Sperry light. Thus, in addition to not being applicable to currents suflicient to form a tongue in the negative flame, the voltage drop is decidedly lower even when the Sperry method is employed at moderate currents and the crater is very different. As explained above, nearly all of the shell is allowed to taper away by the time it reaches the tip so that practically only the core face forms the arc. In addition no deep crater is necessarily formed, the core presenting a shallow concavity at its end of only sufficient depth to hold the bright kernel of the flame.

By employing the above new method of operating a searchlight are, it is possible to double the intrinsic brilliancy obtainable with an ordinary arc with the same amperes flowing and at the same time use less power.

Having described my invention, what I claim and desire to secure by Letters Pat-' ent is:

1. The method of operating electrodes for projectors at moderate amperage in which the positive electrode is provided with a core containing light emitting admixtures which consists in causing such a spindling of said electrode that the crater face operates at an abnormal current density and in positioning the negative electrode at such an angle to the positive that the negative flame sweeps past said crater face without enveloping the electrode back of said face.

2. The method of operating electrodes for projectors at moderate amperage and voltage in which the positive electrode is provided with a core containing light emitting admixtures which consists in causing such a spindling'of said electrode that the crater face operates at an abnormal current den-" sity and in positioning the two electrodes at such an angle to one another that the negative" flame touches the positive electrode only at said crater face. i

3. The method of operating flaming arc electrodes at an amperage. insufficient to produce a negative tongue which consists in positioning the negative electrode at such an angle as to produce a substantially vertical arc flame and in so positioning the positive electrode that the crater face only touches the flame.

4:. The method ofoperating flaming arc electrodes at moderate amperage and voltage which consists in positioning the electrodes at an angle to one another so that the negative flame sweeps past the positive electrode tip and touches said tip before said flame reaches its broadest portion. 1

5. The method of operating electrodes for projectors at moderate amperage in which the positive electrode is provided with a core containing light emitting admixture,

which consists in operating said electrodes at sufiicient current density to cause such a spindling .of the electrode that substantially only the core is exposed at the arcing end, and in confining the crater to the exposed .core face by positioning the two electrodes at such an angle so that the negative flame sweeps past the positive tip without enveloping it.

6. The method of operating flaming arc cored electrodes at an amperage insufficient to produce a negative tongue which consists in directing the negative flame at such an angle as to produce a substantially vertical flame and in so positioning the positive electrode that the cored crater face touches said flame.

In testimony whereof I have afliXed my signature.

PRESTON R. BASSETT. 

